The present invention relates to microwave wafer probes, and particularly to such probes having replaceable probe tips.
Microwave wafer probes are well known to the art as exemplified by probe cards marketed by Tektronix Inc. of Beaverton, Oreg., and by cantilevered probes marketed by Cascade Microtech, Inc. of Beaverton, Oreg. and shown in U.S. Pat. No. 4,697,143. Most existing wafer probes have nonreplaceable transmission line probe tips permanently connected to connector assemblies which in turn detachably connect to external transmission lines linked to test equipment. However, wafer probes having cantilevered tips which are detachably connected to such connector assemblies are also known, thereby enabling replacement of a damaged or worn probe tip without replacing the entire probe head. Prior examples of replaceable probe tips include a coplanar probe tip detachably interconnected with a coaxial connector assembly in a probe marketed by Design Technique International, Inc. of Chatsworth, Calif. Also, Cascade Microtech, Inc. of Beaverton, Oreg. has previously marketed a wide probe having a coplanar probe tip detachably connected to a microstrip "fanout" assembly which in turn is connected to multiple coaxial connectors, as shown in U.S. Pat. No. 4,764,723.
It is often desirable that the wafer probe be equipped with passive electrical circuit components such as capacitors, and/or active components such as amplifiers, to accomplish predetermined probing functions. Such components have previously been mounted directly on probe tips of either the permanent or replaceable type. Unfortunately, in either case, damage or wear to the probe tip requires replacement not only of the tip but of these expensive circuit components as well. This cost cannot feasibly be avoided by placing the components in a remote location relative to the probe tip because such location results in undesirable phase shifts and signal losses.
Accordingly, what is needed is a probe tip system which makes it possible to replace a damaged or worn probe tip economically without requiring replacement of the aforementioned passive or active electrical circuit components, while compatibly enabling the circuit components to be connected in very close proximity to the probe tip.